1. Field of the Invention
This invention relates to a circular optical reflection apparatus and particularly to a circular optical reflection apparatus for scanner, copier, fax machine and the like that uses light reflecting to get required light path for forming desired image.
2. Background of the Invention
Optical devices such as scanner, copier, high resolution fax machine or camera and video camera usually have an optical means to capture an object image. In to principle, a light source emits light ray which is projected to the object. Light ray then reflects from or passes through the object and being directed to a lens to form a light image on an image forming means such as a charged couple device (CCD) or negative film.
In the aforesaid process, it needs an optical path means to direct light ray for a number of reflection or refraction to get a desired light distance (or also referred as TT; Total Track of light path) for forming a good quality image through the lens.
FIG. 1 shows a conventional reflection optical scanner 1 which has a light source 10 emitting light ray to an object (not shown in the picture) laid on a document board 11. Light reflects from the object and enters an optical reflection means 12 which reflects light a number of times to reach a desired optical path then projects light ray to a lens set 13 which in turn forms an object image on a CCD 14. There is a transmission means 15 to move the light source 10 and optical reflection means 12 along a guide rail 16 for scanning the object.
FIG. 2 shows a conventional optical reflection means which includes a plurality of independent reflection mirrors 21 and 22 fixedly located in the optical reflection means with selected relative angles. Incident light may travel into the optical reflection means and reflect among the reflection mirrors 21 and 22 to get a desired optical path. In practice, the optical reflection means usually needs three or four reflection mirrors. Each mirror has a unique position and angle. A slight deviation or error of the position or angle, particularly for the first reflection mirror 21, may result in poor final image quality.
Each reflection mirror has a tolerance in the position and angle that allows the deviation within an acceptable range. However that tolerance will be accumulated after light travels among the reflecting mirrors. The accumulated tolerance could become so large and makes final image quality become very poor.
Many optical devices such as scanners need a relative long optical path. It means the reflection mirrors should be organized with relative large distance among each other. The size of the optical means thus become bulky and heavy. It is against the contemporary trend which highly values compact size and light weight. Another It alternative is trying to reduce size by increase reflection mirror number. Then the weight of the optical means will be increased. Furthermore arrangement of position and angle for a greater number of mirrors becomes even more difficult and time consuming. Accumulated tolerance effect becomes even more worse. Light intensity diminishing effect after reflecting among multiple mirrors become more severe. All of this have negative impact on image quality.
FIG. 3 shows another prior art which uses a polygonal prism reflection means which includes a polygonal prism 31 which has side planes 32, 33, 34, 35 and 36 formed with selected angles therebetween. Side planes 33 and 35 are coated by reflective material 331 and 351 respectively so that they become reflective planes. Side planes 32, 34 and 36 remain transparent. An incident light projects to the prism 31 through the plane 32 normally and being reflected by the plane 33, 35 and being exit through the plane 36. Hence one prism may replace multiple number of reflection mirrors to obtain a required optical path.
However the prism reflection means has drawbacks. There will be unavoidable tolerance when producing the side planes 32, 33, 34, 35 and 36, and consequently will create accumulated tolerance. It will adversely affect image quality especially when the first reflection plane 33 has relatively large tolerance. Furthermore once made, the positional and angular relationship among the planes cannot be changed or adjusted like the mirrors. Its optical path is fixed and unadjustable. Its application is very limited. Different prism should be made for different device or application, and cannot be modularly produced or interchanged. It thus adds a lot of problems and restriction in product design, production and inventory control and management.
In view of aforesaid disadvantages, it is therefore an object of this invention to provide a circular optical reflection apparatus that can greatly reduce reflection mirror number to attain an required optical path with less reflecting angle accumulated tolerance and less component number for reducing cost and product size.
It is another object of this invention to provide a circular optical reflection apparatus in which one circular optical means may produce different optical path by adjusting its position related to incident light direction. Hence one circular optical means may suit for different type and size of optical devices. Product design and development cost may be greatly reduced. Component inventory cost may also become lower.
The circular optical reflection apparatus according to this invention includes a cylindrical reflection member coated with a reflection material on the external surface. The cylindrical reflection member has an axial indent cutaway section to receive and exit light. Incident light entered into the cylindrical means will be reflected inside for a number of times until a desired optical path is reached then be exited for the follow on usage.